Oil Spill Damage: Effects on Marine and Terrestrial Ecosystems

Introduction: The Scale of Oil Spill Damage

The effects of oil spills have had lasting consequences on both marine and terrestrial ecosystems, damaging the respiratory, food chain, and reproductive systems of wildlife for decades. As one researcher notes, "human activity has depleted marine species by 90%, seagrass and wetland habitat by 65%, and degraded water quality 10–1,000 fold" (Narisimha, n.d.). A major portion of these statistics is attributable to oil spills. It has been difficult for scientists to measure the actual effects of any single oil spill, because its consequences can persist across decades. There have been more than 320 known offshore drilling oil spills since 1964 alone (A Deadly Toll, 2011).

The 2010 BP Gulf Oil Spill

On April 20, 2010, BP spilled 205.8 million gallons of oil and 225,000 tons of methane into the Gulf of Mexico over a three-month period, creating one of the largest oil spills in U.S. history (A Deadly Toll, 2011). Recovery efforts cleaned up only approximately 25% of the spilled oil, leaving roughly 75% to be addressed through chemical dispersants used to break up the oil hydrocarbon particles. Nearly two million gallons of toxic dispersants were sprayed into the ocean for this purpose.

The total effects of the BP Deepwater Horizon oil spill are still not fully known and may never be. At the time of the three-month incident, the spill was documented to have caused the deaths of at least 102 species of birds, 6,000 sea turtles, 25,900 marine mammals, and an unknown number of fish. A year later, dead turtles, marine mammals, birds, and fish were still washing ashore on beaches. These counts reflect only animals that reached shore and were recorded — they do not account for animals that sank to the ocean floor or decomposed at sea. There is no reliable way to determine exactly how many animals died from the oil spill versus other causes, particularly in cases where carcasses were oil-coated.

Impacts on Wildlife and Marine Mammals

Oil alone has significant negative impacts on mammals (Oil Spill Impacts on Mammals, n.d.). Direct contact with oil causes chemical burns and skin irritation. Ingestion of oil particles leads to ulcers and internal bleeding. Surface oil emits fumes that mammals inhale when they swim to the surface, causing respiratory problems. The baleen — the filtering structure in the mouths of toothless whales that separates prey from ingested water — becomes coated and ineffective when exposed to oil particles. Prey animals absorb oil particles, which are then passed up the food chain to mammals that feed on them.

Terrestrial mammals, including river otters, mink, and swamp rabbits, lose habitat and food sources as oil washes into coastal wetlands. Oil particles also interfere with reproductive systems, slowing the recovery of affected species.

Conclusion: Long-Term Ecological Consequences

The impact of oil spills on marine and terrestrial ecosystems has been long-lasting, and the total effects remain immeasurable. Oil spills alone cause damage that persists for decades, but cleanup efforts using dispersants add further, equally uncertain damage on top of that. With significant gaps in dispersant testing, there is no reliable basis for fully understanding their actual harm or long-term effects. While dispersants do break up hydrocarbon particles and reduce risk to water surface animals, those animals are still affected indirectly through increased risk to the water column organisms they rely on for food.

Although species are capable of reproducing and replenishing their populations, recovery has been slow because of the damage done to reproductive systems by oil exposure. As additional oil spills have occurred over the years, cumulative losses have grown, making recovery progressively more difficult. Given the compounding effects of oil spill damage — including the destruction of food chains, impairment of reproductive systems, and the uncertain consequences of dispersant use — full ecological recovery will be a long and gradual process.